The recruited patients will meet the chief investigator for a thorough explanation on the trial, emphasizing the fact that the surgery itself is not the essence of this trial. After signing an informed consent for participating in the trial, the patients will be randomly split into two groups. The recruited patients will receive a prescription for antibiotics and how to take them: amoxicillin-clavulanate 875mg twice a day starting at the morning of surgery. Patient with penicillin allergy will receive a loading dose of clindamycin 300mg, followed by 150mg every 6 hours. The duration of treatment (one day or seven days post-operatively) will be determined according to the group attribution.